Exhaust Problem

[famlycar]

I don't know anything about exhaust systems. How to know when an exhaust system (muffler, cat converter, etc.) needs replaced? I have a 96 DX with 175,000 miles. Thanks.

[badbrakes]

Hey Famlycar,

I think they exhaust system is pretty resilient on these. My corolla has seen 15 canadian winters and the only thing I had to replace was the flex pipe. The flex pipe connects right into the exhaust manifold. To answer your question, on my car, it simply started making noise... no apparent fissure or rust thorugh... however at the junction where it flexes, the pipe is vulnerable to wear and small cracks will develop. Fairly easy to repair it yourself.... may be a bit rusted or seized but just go with the penetrating spray the night before and be patient when dismatling (at the manifold that is). At the other end of the flex pipe, you can just saw off the fasteners as they probably will be corroded beyond recognition.

why are you asking ? - Is your car louder recently ?

[famlycar]

Thanks for the feedback! My wife is complaining about some bad odor. I can't notice it but, of course, I drive it most of the time. It did pass the smog test last month if this means anything or not.

I was thinking about taking it to a muffler shop for an extimate but they're probably not going to give me an honest answer.

[badbrakes]

mmmmm.... my first thoughts is that it's not exhaust related. If you had a fissure somewhere in the exhaust system, you'd hear it. Also the exhaust is totally exterior to the car.... it attaches to the manifold and comes out at the back... only exception is one O2 sensor behind the cat converter that has it's electric connector 'enter' the car underneath the passenger seat.... if there's damage there maybe fumes could enter the car... although this is rather an unlikely scenario. If it were me, I'd check first the firewall and make sure all is sealed, (AC, vents, hoses, fan, etc).

[famlycar]

My wife only smells the odor when outside the car. I guess there is some odor now that I'm checking out the problem more. There doesn't seem to be anything rusty or bent anywhere I can tell.

Now, the O2 sensor is probably something I should replace. I changed the one in front of the engine in 2006 and got much better gas mileage but the other one you mentioned I heard about from someone on this forum a while back. Is it easy to change and just about how much it cost for the part? Also, what is the main function of this sensor?

A carload of thanks for the advice!

[badbrakes]

The O2 sensor (both of them actually) is dirt simple to replace. You'll have to take the passenger seat out... but that's simply 4 bolts. The electric connector is underneath the seat and under the carpet if I remember well... that's why you need to take the seat out. The sensor may be a bit seized. Try running the engine a little while and get the exhaust pipe hot - could help to undo it. I use an O2 sensor socket - about 10$. The part if I remember well is about 200$. However, typically a faulty sensor will throw a check engine light... so it may not need replacement... mine went simply cause I hit debris on the highway which took the O2 sensor out. As to your question around its function, I couldn't tell you exactly other than it probably measures what comes out of the cat converter and sends back to computer --- if that doesn't happen, check engine will come on. BTW, if in California, you may have 3 sensors... not sure about that though.
As to your original problem around odor, have you checked the fuel delivery as well ?

[usedranger]

What kind of odor? Rotten egg smell (contaminated gas/bad cat conv)? Burning bacon/oil smell...leaking valve cover gasket?
Really pungent odor, possible a trans leak. A sickening sweet smell, possibly an anti freeze leak. Hot brake pads? In What location is it concentrated at?